Oil filter 2101-1012005 available from the Automotive Units and Accessories Works in Livny, Russian Federation (LAAZ) is extensively known to comprise a casing and a cover held together, and a filter element enclosed in the casing and intended for both coarse and fine oil cleaning, provided with an antidrain and relief valves (cf. "Motor Vehicles "VAZ" by V. A. Vershigora et al., Moscow, Transport PH, 1974, pp.48, 49 (in Russian).
However, the filter mentioned above suffers from the constructional disadvantage that it fails to provide a quality oil cleaning.
During the cold start of an engine only that part of the filter element is involved in operation which effect coarse oil cleaning, since thickened oil fails to pass through the fine-cleaning part of the filter.
Once the engine has warmed up, the fine-cleaning part of the oil filter gets operative; however, coarse oil cleaning in the filter element does not cease, while the main flow of warmed-up oil keeps passing through the coarse-cleaning filter element and the fine-cleaning filter element remains inoperative.
Moreover, whenever the relief valve starts operating, the oil passing therethrough is not cleaned whatever.
Known in the prior art is a sectional-construction oil filter, comprising a casing and a cover joined together, said casing accommodating an antidrain valve and a fine oil cleaning filter element alone with a relief valve and a spring (SU, A, 1,358,985), and a similar but nonsectional filter 2105-1012005 available from LAAZ (cf. Motor Cars VAZ-2108 "Sputnik". Design. Repairs", Moscow, Transport PH, 1987, pp.11, 35 (in Russian).
When cold starting the engine equipped with the aforementioned oil filters, or in the case of a clogged filter element, uncleaned oil soiled with metal particles and carbon deposit is free to pass through the relief valve to get in the engine main manifold. This results, first and foremost, in abnormally rapid wear on the shells of the crankshaft main and crankpin bearings and on the engine piston group, and in that the engine lubricating system is not virtually protected against penetrating said oil contaminants thereinto.
Known in the art is also an oil filter by A. N. Koltunov (RU, A, 1,814,564) which is the closest to the filter proposed herein and comprises a casing joined together with a cover, an antidrain valve, a filter element, a relief valve with a coarse cleaning filter element, and a spring. However, use of such a filter construction under conditions of a heavily dust-laden or dirtied atmosphere, or use of poor-quality oil results in premature clogging of the filter element. The aforediscussed filter construction is adopted as the prototype.